Biomass Dynamics of Biomass Dynamics of Amazonian Forest Amazonian Forest

FragmentsFragments

William F. Laurance William F. Laurance

& Henrique Nascimento& Henrique Nascimento

Smithsonian Tropical Research Institute, PanamaSmithsonian Tropical Research Institute, Panama

Biological Dynamics of Forest Fragments Project, Biological Dynamics of Forest Fragments Project, Manaus, BrazilManaus, Brazil

Deforestation in Brazilian AmazoniaDeforestation in Brazilian Amazonia

Increased Increased significantly significantly during the last during the last decadedecade-1990-1994: 1.31 -1990-1994: 1.31 million ha/yearmillion ha/year

-1995-2002: 1.92 -1995-2002: 1.92 million ha/yearmillion ha/year

0

0.5

1

1.5

2

2.5

3

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Def

ores

tatio

n ra

te (X

10

6 h

a yr

-1)

Year

Rapid Forest FragmentationRapid Forest Fragmentation Every kmEvery km22 of of

each landscape each landscape has 1.3-1.8 km has 1.3-1.8 km of forest edgeof forest edge

Nearly 20,000 Nearly 20,000 km of new edge km of new edge created in created in Brazilian Brazilian Amazon Amazon annually*annually*

* W. Chomentowski, D. Skole, * W. Chomentowski, D. Skole, M. Cochrane, Michigan State M. Cochrane, Michigan State UniversityUniversity

Biological Dynamics of Forest Fragments Biological Dynamics of Forest Fragments ProjectProject

Study AreaStudy Area

Edge-related Changes in Edge-related Changes in Forest Dynamics, Structure, Forest Dynamics, Structure, and Compositionand Composition

Elevated Tree MortalityElevated Tree Mortality

0.5

1

1.5

2

2.5

3

3.5

4

4.5

100 1000

Y = 3.64 - 0.75 log XR=0.51, P=0.0002

Mor

talit

y (%

/yea

r)

Distance to edge (m)

Laurance et al. (1998) Ecology

Loss of Large-tree BiomassLoss of Large-tree Biomass

-100

-80

-60

-40

-20

0

20

100 1000

Y = -52.9 + 18.8 log XR=0.44, P=0.001B

iom

ass

chan

ge (M

g/ha

)

Distance to edge (m)

Laurance et al. (1997) Science

Laurance et al. (2000) Nature

GoalsGoals• To assess impacts of fragmentation on To assess impacts of fragmentation on

all components of aboveground all components of aboveground biomassbiomass• Large (Large (>>10 cm dbh) trees10 cm dbh) trees• Understory biomass Understory biomass • NecromassNecromass

• To estimate effects on forest C storage To estimate effects on forest C storage and atmospheric emissionsand atmospheric emissions

Biomass ParametersBiomass Parameters

•Downed coarse debris (Downed coarse debris (>>10 cm)10 cm)

•Downed fine debris (2.5-9.9 cm)Downed fine debris (2.5-9.9 cm)

•SnagsSnags

•Litter (leaves, twigs, fruits, etc.)Litter (leaves, twigs, fruits, etc.)

•Annual production of wood debrisAnnual production of wood debris

•Turnover of wood debrisTurnover of wood debris

Large-tree biomassLarge-tree biomass NecromassNecromass

•Seedlings (<1 cm)Seedlings (<1 cm)

•Saplings (1-4.9 cm)Saplings (1-4.9 cm)

•Small trees (5-10 cm)Small trees (5-10 cm)

•Stemless palmsStemless palms

•Lianas (Lianas (>>1 cm)1 cm)

Understory biomassUnderstory biomass

•Large-tree biomassLarge-tree biomass

•Biomass incrementBiomass increment

•Annual change in biomassAnnual change in biomass

Ordination of 14 Biomass Ordination of 14 Biomass AttributesAttributes

-1.5

-1

-0.5

0

0.5

1

1.5

2

-1.2 -0.8 -0.4 0 0.4 0.8 1.2 1.6

Edge plotsInterior plots

Axi

s 2:

less

deb

ris-

->

Axis 1: more tree mortality, debris, small trees-->

Edge vs. Interior: Significant DifferencesEdge vs. Interior: Significant Differences

0 10 20 30 40 50 60 70 80

Total necromass

Small-tree biomass

FWD stock

CWD turnover

CWD stock

CWD production

Biomass increment

Tree mortality

Increase (%)

Increased Wood DebrisIncreased Wood Debris

0

2

4

6

8

10

12

100 1000

Y = 10.87 - 2.30 log XR=0.60, P<0.0001

CW

D p

rodu

ctio

n (M

g/ha

/yea

r)

Distance to edge (m)

Nascimento & Laurance, in press. Ecological Applications.

Increased LitterIncreased Litter

5

6

7

8

9

10

11

12

13

100 1000

Y = 9.46 - 0.67 log XR=0.28, P<0.05

Bio

mas

s (M

g/h

a)

Distance to edge (m)

Nascimento & Laurance, in press.

Ecological Applications.

Biomass of Small (5-10 cm dbh) TreesBiomass of Small (5-10 cm dbh) Trees

10

12

14

16

18

20

22

100 1000

Y = 18.12 - 1.35 log XR=0.39, P=0.005

Bio

mas

s (M

g/ha

)

Distance to edge (m)

Total Understory BiomassTotal Understory Biomass

20

25

30

35

40

45

100 1000

Y = 34.1 - 1.2 log XR=0.19, N.S.

Bio

mas

s (M

g/ha

)

Distance to edge (m)

Estimating Edge-related Estimating Edge-related Carbon EmissionsCarbon Emissions

Assume no changes in belowground biomassAssume no changes in belowground biomass Net biomass decline = biomass lost from large trees Net biomass decline = biomass lost from large trees

(22.7 Mg/ha) – increases in understory biomass (1.7 (22.7 Mg/ha) – increases in understory biomass (1.7 Mg/ha) and necromass (10.1 Mg/ha) = 10.9 Mg/haMg/ha) and necromass (10.1 Mg/ha) = 10.9 Mg/ha

Half of biomass is carbon, most is respired quicklyHalf of biomass is carbon, most is respired quickly Thus, committed emissions are 4-6 Mg/haThus, committed emissions are 4-6 Mg/ha Because tree mortality is elevated within 300 m of Because tree mortality is elevated within 300 m of

edges, we expect 12-18 Mg C for every 100 m of edges, we expect 12-18 Mg C for every 100 m of forest edge createdforest edge created

Based simply on current rate of edge creation, annual Based simply on current rate of edge creation, annual emissions would be 2.3-3.5 million Mg/yearemissions would be 2.3-3.5 million Mg/year

Fragmentation and FireFragmentation and Fire Increased wood debris & litterIncreased wood debris & litter Recurring canopy damageRecurring canopy damage Higher insolation, wind & Higher insolation, wind &

temperaturestemperatures Nearby ignition sourcesNearby ignition sources

0

5

10

15

0 1000 2000 3000 4000

Surface fires at Tailândia, Brazil

Fir

e f

req

uen

cy

(n

o./c

en

tury

)

Distance to edge (m)

ConclusionsConclusions Fragmentation causes striking Fragmentation causes striking

changes in the distribution of changes in the distribution of aboveground biomassaboveground biomass– Decline of large-tree biomassDecline of large-tree biomass– More wood debris, litter, small More wood debris, litter, small

treestrees

C cycling accelerates sharplyC cycling accelerates sharply Substantial C emissionsSubstantial C emissions Drastic increase in fire Drastic increase in fire

vulnerabilityvulnerability